Question

How should I go about providing download functionality on an asp.net page to download a series of rows from a database table represented as a linq2sql class that only has primitive types for members (ideally into a format that can be easily read by Excel)?

E.g.

public class Customer
{
public int CustomerID;
public string FirstName;
public string LastName;
}

What I have tried so far.

Initially I created a DataTable, added all the Customer data to this table and bound it to a DataGrid, then had a download button that called DataGrid1.RenderControl to an HtmlTextWriter that was then written to the response (with content type “application/vnd.ms-excel”) and that worked fine for a small number of customers.

However, now the number of rows in this table is >10,000 and is expected to reach upwards of 100,000, so it is becoming prohibitive to display all this data on the page before the user can click the download button.

So the question is, how can I provide the ability to download all this data without having to display it all on a DataGrid first?

Answer 1

So after a bit of research, the solution I ended up trying first was to use a slightly modified version of the code sample from http://www.asp.net/learn/videos/video-449.aspx and format each row value in my DataTable for CSV using the following code to try to avoid potentially problematic text:

private static string FormatForCsv(object value)
        {
            var stringValue = value == null ? string.Empty : value.ToString();
            if (stringValue.Contains("\"")) { stringValue = stringValue.Replace("\"", "\"\""); }
            return "\"" + stringValue + "\"";
        }

For anyone who is curious about the above, I’m basically surrounding each value in quotes and also escaping any existing quotes by making them double quotes. I.e.

My Dog => "My Dog"
My "Happy" Dog => "My ""Happy"" Dog"

This appears to be doing the trick for now for small numbers of records. I will try it soon with the >10,000 records and see how it goes.

Edit: This solution has worked well in production for thousands of records.